Height-Adjusting Assembly for Office Chair Backrest

ABSTRACT

A height-adjusting assembly for an office chair backrest includes a supporting unit mounted with a vertically movable backrest. The supporting unit and the backrest have correspondingly an engaging element and a series of positioning teeth, respectively, to be coupled mutually. Upper and lower ends of the series of positioning teeth have a retracting portion and an expanding portion for retracting and expanding the engaging element, respectively. When the backrest slides upward, the engaging element successively engages with one of the positioning teeth so as to position the backrest at a desired height. When the backrest reaches to an upmost position, the engaging element is pressed by the retracting portion and retracts so as to separate from the positioning teeth. Then the backrest reaches a bottommost position thereof has the engaging element expanded by the expanding portion, thereby allowing the engaging element to engage with the positioning teeth again.

FIELD OF THE INVENTION

The present invention relates to a height-adjusting assembly for anoffice chair backrest, wherein a supporting unit mounted with avertically movable backrest is fixed to a chair, while at least a seriesof positioning teeth and an engaging element that are configured toresiliently couple with each other are provided between the supportingunit and the backrest for allowing the backrest to vertically slidealong and get positioned with respect to the supporting unit.

BACKGROUND OF THE INVENTION

Since modern people spend much more time in their offices then at home,whether an office chair is comfortable enough has become a majorconcern. In view of low back pain caused by long-term, constant sittingposture, some waist-protecting devices purported to be effective inpreventing low back pain have been seen in the market. However, whilethe effectiveness of most of these waist-protecting devices has not beenproven, excessive dependency on such waist-protecting devices may bringabout adverse effects. Thus, for protecting people always stayingsitting in work, such as computer users, from low back pain, anappropriate chair is necessary.

Generally, to a sitter, his/her intervertebral disks in the lumbarvertebra bear more pressure when the body remains vertical or slightlyinclining forward (with an included angle between his/her thighs andupper part of body smaller than 90 degrees) then when he/she stands.Besides, the long-term still sitting posture (lacking for change inposture) is likely to result in the sitter's tiredness. Thus people tendto frequently move after long-term sitting for mitigatinguncomfortableness. A chair with a backrest can facilitate supportinghuman body and relaxing the lumbar vertebra as well as muscles and isalso helpful in supporting the waist, thereby preventing low back pain.

However, chairs can only provide these functions when properly designed.Otherwise, an excessive sitting depth may hinder the lumbar vertebrafrom contacting the backrest and in turn from getting supported. In someother cases, a backrest positioned excessively high or low can similarlyowe the lumbar vertebra proper support.

SUMMARY OF THE INVENTION

Hence, in order to solve the problem of the prior art where the chairbackrest fails to be properly settled in height to support a sitter'sback and waist, the present invention provides a structure which allowsa backrest to be freely adjusted in height, so as to ensure a sitter'sback and waist with optimal support.

The technical means adopted by the present invention for solving theabove problem includes a supporting unit fixed to a chair and a backrestwhich is configured to vertically slide along and get positioned withrespect to the supporting unit, wherein the supporting unit is providedwith at least one series of positioning teeth while the backrest has anengaging element for resiliently engaging with the positioning teeth.The engaging element is formed with a socket portion for correspondingand coupling with a plug portion formed on the backrest. Meantime, anupper end and a lower end of each said series of positioning teeth areformed with a retracting portion for retracting the engaging element andan expanding portion for expanding the engaging element.

In addition, a waist-rest portion is pivotally attached below thebackrest of the present invention for providing resilient support.

Thereby, when the backrest of the present invention vertically slidesfrom upward, the engaging element equipped thereto successively engageswith one said positioning tooth of the supporting unit, so as toposition the backrest at a desired height. When the backrest reaches itsupmost position, the engaging element is pressed by the retractingportion on the supporting unit so that the engaging element swings toretract and the backrest can be then lowered to a bottommost positionthereof to have the engaging element re-expanded by the expandingportion on the supporting unit, thereby again being capable ofresiliently coupling with the positioning teeth.

Thus, the present invention would be well understood and implementedaccording to the embodiment in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the present invention.

FIG. 2 is an exploded view of a backrest according to the presentinvention.

FIG. 3 is a partially enlarged view of the area encircled by Circle A inFIG. 2.

FIG. 4 illustrates how the backrest and a supporting unit are combined.

FIG. 5 is a partial front view of the present invention.

FIG. 6 is a partially enlarged view of the area encircled by Circle B inFIG. 5.

FIG. 7 shows the backrest positioned at an upmost position.

FIG. 8 shows the backrest positioned at a bottommost position.

FIG. 9 is a schematic drawing of the present invention wherein anengaging element is expanded.

FIG. 10 is a schematic drawing illustrating operation of a waist-restportion according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1, 2, 3 and 4, the present invention has a supportingunit 1 assembled to a chair and a backrest 2 that is mounted on thesupporting unit 1 and configured to vertically slide along and getpositioned with respect to the supporting unit 1. The supporting unit 1is a frame of a reversed-U shape and has two facing inner laterals eachformed with a series of positioning teeth 11 so that the two series ofpositioning teeth 11 corresponding to each other. At an upper end and alower end of each said series of positioning teeth 11, a retractingportion 12 and an expanding portion 13 are provided, respectively. Inaddition, two front laterals of the supporting unit 1 are each providedwith a guiding groove 14.

Moreover, on the backrest 2 at where corresponds to the positioningteeth 11 of the supporting unit 1, sliding portions 21 are provided forconnecting with the supporting unit 1. Each of the sliding portions 21further includes a recessed part 211 formed on the backrest 2 and acover 212 for combining with and covering the recessed part 211 so thata space is defined between the recessed part 211 and the cover 212 forthe supporting unit 1 to piercing therethrough. Besides, a raisedguiding portion 213 is formed at an inner side of the cover 212 forslidably coupling with the guiding groove 14 of the supporting unit 1.Meantime, an engaging element 22 is pivotally fixed to the slidingportion 21 near the positioning teeth (i.e. on the recessed part 211)such that the engaging element 22 is able to freely swing. A spring 23is provided to resiliently push the engaging element 22 outward so as torightly make a free end 221 of the engaging element 22 resilientlyengaged with any of the positioning teeth 11 on the supporting unit 1.The engaging element 22 is further formed with a socket portion 222while the sliding portion 21 (i.e. the recessed part 211) has a plugportion 214, so that when the engaging element 22 is engaged, the plugportion 214 is fittingly inlaid to and thus positioned with respect tothe socket portion 222 thereof.

Additionally, a waist-rest portion 3 is attached below the backrest 2 bymeans of pivotally fixing portions 20, 30 and a pivot 4 passingtherethrough. The pivot 4 is mounted therearound with a plurality ofsprings 5, wherein each of the springs 5 has two ends abutting againstthe backrest 2 and the waist-rest portion 3, thereby allowing thewaist-rest portion 3 to resiliently swing in a predetermined direction.

Therefore, as shown in FIGS. 5 and 6, when height adjustment of thebackrest 2 is desired, by easily pushing the backrest 2 upward, theengaging element 22 resiliently pushed can spring to successively makeits free end 221 retained in the positioning teeth 11 of differentheights, so that the backrest 2 can be moved to and positioned atdifferent heights. Then referring to FIG. 7, when the backrest 2 ispushed to a predetermined upmost position, the engaging element 22 ispressed by the retracting portion 12 at the upper end of the series ofthe positioning teeth 11 and forced to swing rightward so that thesocket portion 222 thereon is coupled with the plug portion 214 and getpositioned. At this time, the backrest 2 can freely slide downward.Afterward, as shown in FIGS. 8 and 9, when the backrest slides to apredetermined bottommost position, the free end 221 of the engagingelement 22 comes to abut against the expanding portion 13 and is pushedleftward, so that the socket portion 222 of the engaging element 22 isdecoupled from the plug portion 214 and then returns to its resilientengagement with any of the positioning teeth 11 due to the pushing forcefrom the spring 23. Consequently, the backrest 2 is allowed to bereadjusted in height from lower to higher.

At last, as shown in FIG. 10, when the backrest 1 is adjusted to thedesired height, the waist-rest portion 3 is rightly positioned toproperly support a waist of a sitter on the chair, thereby providing thesitter's waist with comforting support.

1. A height-adjusting assembly for an office chair backrest, comprisinga supporting unit fixed to a chair for allowing a backrest to be mountedthereon, therein: the supporting unit being a frame provided with atleast one series of positioning teeth, wherein an upper end and a lowerend of the series of positioning teeth are provide with a retractingportion and an expanding portion, respectively; the backrest having atleast one sliding portion corresponding to the series of positioningteeth of the supporting unit, and an engaging element pivotally fixedthereto for resiliently coupling with any of the positioning teeth,wherein the engaging element and the sliding portion havecorrespondingly a socket portion and a plug portion to be coupled witheach other while the retracting portion and the expanding portion of thesupporting unit serve to retract and expand the engaging element,respectively, so as to make the socket portion and the plug portionengaged or separated.
 2. The height-adjusting assembly of claim 1,wherein the sliding portion on the supporting unit includes a recessedpart formed on the backrest and a cover, which such covers the recessedpart that a space is defined between the recessed part and the cover forallowing the supporting unit to pass therethrough.
 3. Theheight-adjusting assembly of claim 1, wherein a waist-rest portion ispivotally attached below the backrest for providing resilient support.